Gene expression analysis reveals matrilysin as a key regulator of pulmonary fibrosis in mice and humans

Peripheral blood biomarkers in idiopathic pulmonary fibrosis

In this article, we review the evidence for peripheral blood biomarkers in idiopathic pulmonary fibrosis (IPF), a life-threatening fibrotic lung disease of unknown etiology. We focus on selected biomarkers present in peripheral blood, as they are easy to obtain, can be measured longitudinally, and have the greatest likelihood of achieving clinical utility. This article concentrates on biomarkers with mechanistic plausibility that may be directly involved in the development of IPF, including KL-6, surfactant proteins A and D, matrix metalloproteases (MMP) 1 and 7, CCL18, VEGF, YKL-40, osteopontin, circulating fibrocytes, and T cells. After reviewing the evidence base for each, we designate the biomarkers that may have utility as: (1) diagnostic biomarkers to distinguish IPF from other interstitial lung diseases, (2) prognostic biomarkers that are correlated with disease progression or mortality, or (3) biomarkers that can be used as tools for serial monitoring of disease severity. Although there are no validated biomarkers that are currently available, the need for surrogates of diagnosis, prognosis, and monitoring of disease course with emerging therapies is great.

Ventilator-induced lung injury: the role of gene activation

PURPOSE OF REVIEW

Ventilator-induced lung injury (VILI) is a ubiquitous iatrogenic clinical problem in critical care. Aside from avoiding large tidal volumes, little progress has been made in identifying effective clinical strategies to minimize this injury. With recent rapid development in bioinformatics and high-throughput molecular technology, the genetic basis of lung injury has been intensively investigated. This review will describe recent insights and potential therapies developed in the field.

RECENT FINDINGS

Much progress has been made in delineating the possible genes and gene products involved in VILI through various mechanisms such as early induced genes, capillary leak, apoptosis, fibrin deposition, inflammatory cytokines, oxidative stress, disrupted angiogenesis, and neutrophil infiltration. Some studies have translated bench findings to the bedside in an attempt to identify clinically important genetic susceptibility, which could aid in the identification of at-risk individuals who might benefit from careful titration of mechanical ventilation. Genetic insights also provide candidate pharmaceutical approaches that may ameliorate VILI in the future.

SUMMARY

Much relevant information exists for investigators and clinicians interested in VILI. Future research will interlink evolving data to provide a more integrated picture of the molecular mechanisms involved in VILI enabling translation of the most promising candidate therapies.

Cytokine-like factor 1 gene expression is enriched in idiopathic pulmonary fibrosis and drives the accumulation of CD4+ T cells in murine lungs: evidence for an antifibrotic role in bleomycin injury

Idiopathic pulmonary fibrosis (IPF) is a progressive and typically fatal lung disease. To gain insight into the pathogenesis of IPF, we reanalyzed our previously published gene expression data profiling IPF lungs. Cytokine receptor-like factor 1 (CRLF1) was among the most highly up-regulated genes in IPF lungs, compared with normal controls. The protein product (CLF-1) and its partner, cardiotrophin-like cytokine (CLC), function as members of the interleukin 6 (IL-6) family of cytokines. Because of earlier work implicating IL-6 family members in IPF pathogenesis, we tested whether CLF-1 expression contributes to inflammation in experimental pulmonary fibrosis. In IPF, we detected CLF-1 expression in both type II alveolar epithelial cells and macrophages. We found that the receptor for CLF-1/CLC signaling, ciliary neurotrophic factor receptor (CNTFR), was expressed only in type II alveolar epithelial cells. Administration of CLF-1/CLC to both uninjured and bleomycin-injured mice led to the pulmonary accumulation of CD4(+) T cells. We also found that CLF-1/CLC administration increased inflammation but decreased pulmonary fibrosis. CLF-1/CLC leads to significantly enriched expression of T-cell-derived chemokines and cytokines, including the antifibrotic cytokine interferon-γ. We propose that, in IPF, CLF-1 is a selective stimulus of type II alveolar epithelial cells and may potentially drive an antifibrotic response by augmenting both T-helper-1-driven and T-regulatory-cell-driven inflammatory responses in the lung.

Peripheral blood proteins predict mortality in idiopathic pulmonary fibrosis

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease of unknown etiology with a variable and unpredictable course.

OBJECTIVES

The aim of this study was to identify and validate plasma proteins that are predictive of outcome in IPF.

METHODS

Plasma samples were available for 241 patients with IPF (140 derivation and 101 validation). In the derivation cohort, concentrations of 92 proteins were analyzed using a multiplex bead-based immunoassay and concentrations of matrix metalloproteinase (MMP)-7, MMP-1, and surfactant protein D were assessed by ELISA. In the validation cohort concentrations of intercellular adhesion molecule (ICAM)-1, IL-8, and vascular cell adhesion molecule (VCAM)-1 were assessed by bead-based multiplex assay, and S100A12 and MMP-7 by ELISA. Associations of biomarkers with mortality, transplant-free survival, and disease progression were tested in the derivation and validation cohorts using nonparametric methods of survival analysis and the Cox proportional hazards model, and an integrated risk prediction score was derived and tested.

MEASUREMENTS AND MAIN RESULTS

High concentrations of MMP-7, ICAM-1, IL-8, VCAM-1, and S100A12 predicted poor overall survival, poor transplant-free survival, and poor progression-free survival in the derivation cohort. In the independent validation cohort high concentrations of all five were predictive of poor transplant-free survival; MMP-7, ICAM-1, and IL-8 of overall survival; and ICAM-1 of poor progression-free survival. The personal clinical and molecular mortality prediction index derived in the derivation cohort was highly predictive of mortality in the validation cohort.

CONCLUSIONS

Our results suggest that plasma proteins should be evaluated as a tool for prognosis determination in prioritization of patients for lung transplantation and stratification in drug studies.

Evolving genomic approaches to idiopathic pulmonary fibrosis: moving beyond genes

A little more than 10 years ago, the completed sequencing of the human genome boldly promised to usher in an era of enhanced understanding and accelerated development of treatments for most human diseases. Ten years later, many of these therapeutic goals have not been reached, but genomic technologies have dramatically enhanced our understanding of how genes and gene networks contribute to the pathogenesis of disease. In this review, we describe how genomic technologies have shaped our study of idiopathic pulmonary fibrosis (IPF), a devastating, progressive scarring of the lung parenchyma, a disease without a known cause, or treatment. We frame the important genomic discoveries in IPF of the previous decade in the clinical context of establishing a diagnosis of IPF and predicting the prognosis. Gene expression profiling of peripheral blood will help identify potential biomarkers for assessing the clinical severity of IPF. We highlight the growth of epigenetic research in IPF, including the contribution of microRNAs to the pathogenesis of disease. We suggest that the full power of genomic discoveries in IPF will be realized when researchers apply these techniques prospectively in large collaborative studies across institutions, support the training of young investigators in genomics, and employ systems biology approaches to the interpretation of genomic data.

Matrilysin (MMP-7) inhibition of BMP-7 induced renal tubular branching morphogenesis suggests a role in the pathogenesis of human renal dysplasia

Congenital renal dysplasia (RD) is a severe form of congenital renal malformation characterized by disruption of normal renal development with cyst formation, reduced or absent nephrons, and impaired renal growth. The authors previously identified that matrilysin (matrix metalloproteinase-7) was overexpressed in a microarray gene expression analysis of human RD compared to normal control kidneys. They now find that active matrilysin gene transcription and protein synthesis occur within dysplastic tubules and epithelial cells lining cysts in human RD by RT-PCR and immunohistochemistry. Similar staining patterns were seen in obstructed kidneys of pouch opossums that show histological features similar to that of human RD. In vitro, matrilysin inhibits formation of branching structures in mIMCD-3 cells stimulated by bone morphogenetic protein-7 (BMP-7) but does not inhibit hepatocyte growth factor-stimulated branching. BMP-7 signaling is essential for normal kidney development, and overexpression of catalytically active matrilysin in human embryonic kidney 293 cells reduces endogenous BMP-7 protein levels and inhibits phosphorylation of BMP-7 SMAD signaling intermediates. These findings suggest that matrilysin expression in RD may be an injury response that disrupts normal nephrogenesis by impairing BMP-7 signaling.

Genetically manipulated mouse models of lung disease: potential and pitfalls

Gene targeting in mice (transgenic and knockout) has provided investigators with an unparalleled armamentarium in recent decades to dissect the cellular and molecular basis of critical pathophysiological states. Fruitful information has been derived from studies using these genetically engineered mice with significant impact on our understanding, not only of specific biological processes spanning cell proliferation to cell death, but also of critical molecular events involved in the pathogenesis of human disease. This review will focus on the use of gene-targeted mice to study various models of lung disease including airways diseases such as asthma and chronic obstructive pulmonary disease, and parenchymal lung diseases including idiopathic pulmonary fibrosis, pulmonary hypertension, pneumonia, and acute lung injury. We will attempt to review the current technological approaches of generating gene-targeted mice and the enormous dataset derived from these studies, providing a template for lung investigators.

Ligand-independent transforming growth factor-β type I receptor signalling mediates type I collagen-induced epithelial-mesenchymal transition

Evidence suggests epithelial-mesenchymal transition (EMT) as one potential source of fibroblasts in idiopathic pulmonary fibrosis. To assess the contribution of alveolar epithelial cell (AEC) EMT to fibroblast accumulation in vivo following lung injury and the influence of extracellular matrix on AEC phenotype in vitro, Nkx2.1-Cre;mT/mG mice were generated in which AECs permanently express green fluorescent protein (GFP). On days 17-21 following intratracheal bleomycin administration, ~4% of GFP-positive epithelial-derived cells expressed vimentin or α-smooth muscle actin (α-SMA). Primary AECs from Nkx2.1-Cre;mT/mG mice cultured on laminin-5 or fibronectin maintained an epithelial phenotype. In contrast, on type I collagen, cells of epithelial origin displayed nuclear localization of Smad3, acquired spindle-shaped morphology, expressed α-SMA and phospho-Smad3, consistent with activation of the transforming growth factor-β (TGFβ) signalling pathway and EMT. α-SMA induction and Smad3 nuclear localization were blocked by the TGFβ type I receptor (TβRI, otherwise known as Alk5) inhibitor SB431542, while AEC derived from Nkx2.1-Cre;Alk5(flox/KO) mice did not undergo EMT on collagen, consistent with a requirement for signalling via Alk5 in collagen-induced EMT. Inability of a pan-specific TGFβ neutralizing antibody to inhibit effects of collagen together with absence of active TGFβ in culture supernatants is consistent with TGFβ ligand-independent activation of Smad signalling. These results support the notion that AECs can acquire a mesenchymal phenotype following injury in vivo and implicate type I collagen as a key regulator of EMT in AECs through signalling via Alk5, likely in a TGFβ ligand-independent manner.

Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is a devastating, age-related lung disease of unknown cause that has few treatment options. This disease was once thought to be a chronic inflammatory process, but current evidence indicates that the fibrotic response is driven by abnormally activated alveolar epithelial cells (AECs). These cells produce mediators that induce the formation of fibroblast and myofibroblast foci through the proliferation of resident mesenchymal cells, attraction of circulating fibrocytes, and stimulation of the epithelial to mesenchymal transition. The fibroblast and myofibroblast foci secrete excessive amounts of extracellular matrix, mainly collagens, resulting in scarring and destruction of the lung architecture. The mechanisms that link idiopathic pulmonary fibrosis with ageing and aberrant epithelial activation are unknown; evidence suggests that the abnormal recapitulation of developmental pathways and epigenetic changes have a role. In this Seminar, we review recent data on the clinical course, therapeutic options, and underlying mechanisms thought to be involved in the pathogenesis of idiopathic pulmonary fibrosis.

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Bayesian probit regression model for the diagnosis of pulmonary fibrosis: proof-of-principle

Background

The accurate diagnosis of idiopathic pulmonary fibrosis (IPF) is a major clinical challenge. We developed a model to diagnose IPF by applying Bayesian probit regression (BPR) modelling to gene expression profiles of whole lung tissue.

Methods

Whole lung tissue was obtained from patients with idiopathic pulmonary fibrosis (IPF) undergoing surgical lung biopsy or lung transplantation. Controls were obtained from normal organ donors. We performed cluster analyses to explore differences in our dataset. No significant difference was found between samples obtained from different lobes of the same patient. A significant difference was found between samples obtained at biopsy versus explant. Following preliminary analysis of the complete dataset, we selected three subsets for the development of diagnostic gene signatures: the first signature was developed from all IPF samples (as compared to controls); the second signature was developed from the subset of IPF samples obtained at biopsy; the third signature was developed from IPF explants. To assess the validity of each signature, we used an independent cohort of IPF and normal samples. Each signature was used to predict phenotype (IPF versus normal) in samples from the validation cohort. We compared the models' predictions to the true phenotype of each validation sample, and then calculated sensitivity, specificity and accuracy.

Results

Surprisingly, we found that all three signatures were reasonably valid predictors of diagnosis, with small differences in test sensitivity, specificity and overall accuracy.

Conclusions

This study represents the first use of BPR on whole lung tissue; previously, BPR was primarily used to develop predictive models for cancer. This also represents the first report of an independently validated IPF gene expression signature. In summary, BPR is a promising tool for the development of gene expression signatures from non-neoplastic lung tissue. In the future, BPR might be used to develop definitive diagnostic gene signatures for IPF, prognostic gene signatures for IPF or gene signatures for other non-neoplastic lung disorders such as bronchiolitis obliterans.

Activation of the Wnt/β-catenin signaling pathway by mechanical ventilation is associated with ventilator-induced pulmonary fibrosis in healthy lungs

BACKGROUND

Mechanical ventilation (MV) with high tidal volumes (V(T)) can cause or aggravate lung damage, so-called ventilator induced lung injury (VILI). The relationship between specific mechanical events in the lung and the cellular responses that result in VILI remains incomplete. Since activation of Wnt/β-catenin signaling has been suggested to be central to mechanisms of lung healing and fibrosis, we hypothesized that the Wnt/β-catenin signaling plays a role during VILI.

METHODOLOGY/PRINCIPAL FINDINGS

Prospective, randomized, controlled animal study using adult, healthy, male Sprague-Dawley rats. Animals (n = 6/group) were randomized to spontaneous breathing or two strategies of MV for 4 hours: low tidal volume (V(T)) (6 mL/kg) or high V(T) (20 mL/kg). Histological evaluation of lung tissue, measurements of WNT5A, total β-catenin, non-phospho (Ser33/37/Thr41) β-catenin, matrix metalloproteinase-7 (MMP-7), cyclin D1, vascular endothelial growth factor (VEGF), and axis inhibition protein 2 (AXIN2) protein levels by Western blot, and WNT5A, non-phospho (Ser33/37/Thr41) β-catenin, MMP-7, and AXIN2 immunohistochemical localization in the lungs were analyzed. High-V(T) MV caused lung inflammation and perivascular edema with cellular infiltrates and collagen deposition. Protein levels of WNT5A, non-phospho (Ser33/37/Thr41) β-catenin, MMP-7, cyclin D1, VEGF, and AXIN2 in the lungs were increased in all ventilated animals although high-V(T) MV was associated with significantly higher levels of WNT5A, non-phospho (Ser33/37/Thr41) β-catenin, MMP-7, cyclin D1, VEGF, and AXIN2 levels.

CONCLUSIONS/SIGNIFICANCE

Our findings demonstrate that the Wnt/β-catenin signaling pathway is modulated very early by MV in lungs without preexistent lung disease, suggesting that activation of this pathway could play an important role in both VILI and lung repair. Modulation of this pathway might represent a therapeutic option for prevention and/or management of VILI.

Integrating mechanisms of pulmonary fibrosis

Pulmonary fibrosis is a highly heterogeneous and lethal pathological process with limited therapeutic options. Although research on the pathogenesis of pulmonary fibrosis has frequently focused on the mechanisms that regulate the proliferation, activation, and differentiation of collagen-secreting myofibroblasts, recent studies have identified new pathogenic mechanisms that are critically involved in the initiation and progression of fibrosis in a variety of settings. A more detailed and integrated understanding of the cellular and molecular mechanisms of pulmonary fibrosis could help pave the way for effective therapeutics for this devastating and complex disease.

Reduction in serum high mobility group box-1 level by polymyxin B-immobilized fiber column in patients with idiopathic pulmonary fibrosis with acute exacerbation

BACKGROUND/AIM

Recent reports suggest that polymyxin B (PMX)-immobilized fiber may have beneficial effects in idiopathic pulmonary fibrosis (IPF) with acute exacerbation (AE). High mobility group box-1 (HMGB-1) is an important pro-inflammatory mediator that contributes to acute lung inflammation. This study was aimed to investigate whether PMX treatment affects serum HMGB-1 levels and oxygenation in IPF patients with AE.

MATERIALS AND METHODS

Twenty IPF patients with AE were treated by PMX. PMX treatment was carried out once daily for 2 successive days. Serum HMGB-1 levels were measured before and after PMX treatment. We also monitored arterial oxygen tension (PaO(2))/inspiratory oxygen fraction (FiO(2)) (P/F) ratio. PMX fiber columns were analyzed to examine whether HMGB-1 was absorbed by PMX.

RESULTS

PMX treatment significantly improved both the serum HMGB-1 level and P/F ratio. HMGB-1 was detected in washing medium from the PMX column.

CONCLUSION

PMX treatment may reduce serum HMGB-1 and improve oxygenation in patients with IPF with AE.

Matrix metalloproteinase 3 is a mediator of pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) may be triggered by epithelial injury that results in aberrant production of growth factors, cytokines, and proteinases, leading to proliferation of myofibroblasts, excess deposition of collagen, and destruction of the lung architecture. The precise mechanisms and key signaling mediators responsible for this aberrant repair process remain unclear. We assessed the importance of matrix metalloproteinase-3 (MMP-3) in the pathogenesis of IPF through i) determination of MMP-3 expression in patients with IPF, ii) in vivo experiments examining the relevance of MMP-3 in experimental models of fibrosis, and iii) in vitro experiments to elucidate possible mechanisms of action. Gene expression analysis, quantitative RT-PCR, and Western blot analysis of explanted human lungs revealed enhanced expression of MMP-3 in IPF, compared with control. Transient adenoviral vector-mediated expression of recombinant MMP-3 in rat lung resulted in accumulation of myofibroblasts and pulmonary fibrosis. Conversely, MMP-3-null mice were protected against bleomycin-induced pulmonary fibrosis. In vitro treatment of cultured lung epithelial cells with purified MMP-3 resulted in activation of the β-catenin signaling pathway, via cleavage of E-cadherin, and induction of epithelial-mesenchymal transition. These processes were inhibited in bleomycin-treated MMP-3-null mice, as assessed by cytosolic translocation of β-catenin and cyclin D1 expression. These observations support a novel role for MMP-3 in the pathogenesis of IPF, through activation of β-catenin signaling and induction of epithelial-mesenchymal transition.

Elevated MMP-7 levels in patients with systemic sclerosis: correlation with pulmonary involvement

BACKGROUND

Fibrosis is characterized by an excessive accumulation of connective tissue because of an imbalance between synthesis and degradation of extracellular matrix proteins. Systemic sclerosis (SSc) is a prototypic chronic inflammatory disease leading to a severe fibrosis of the skin and many internal organs. QUESTIONS ADDRESSED: We investigated whether serum MMP-7 levels reflect the activity of the fibrotic reaction in systemic sclerosis.

EXPERIMENTAL DESIGN

Serum samples were obtained from 123 patients with systemic sclerosis. MMP-serum levels of all patients with SSc were compared with age-matched healthy controls.

RESULTS

Significantly increased median serum MMP-7 levels were found in patients with SSc when compared with controls. The median MMP-7 serum level of patients with lung fibrosis (LF) was significantly higher compared with those without LF. Accordingly, patients with dyspnea and DLCO (diffusion capacity of the lung for carbon monoxide) levels below 60% showed significantly higher median MMP-7 levels.

CONCLUSIONS

Elevated MMP-7 levels are associated with an advanced stage of SSc and LF. These data suggest that in SSc MMP-7 is involved in the process of fibrotic tissue remodelling.

Blockade of the Wnt/β-catenin pathway attenuates bleomycin-induced pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease and characterized by abnormal growth of fibroblasts and lung scarring. While the pathogenesis of IPF is not clearly understood, activation of transforming growth factor-β (TGF-β) and disruption of alveolar basement membrane seem to play important roles in leading to excess disruption of the matrix, which is associated with activated matrix metalloproteinase (MMP) and aberrant proliferation of myofibroblasts. The Wnt/β-catenin pathway is an important regulator of cellular proliferation and differentiation and abnormal activation of Wnt/β-catenin signal was observed in IPF. We examined whether inhibition of the Wnt/β-catenin pathway could attenuate pulmonary fibrosis in a bleomycin-induced murine model of pulmonary fibrosis. Pulmonary fibrosis was induced in C57BL/6N mice by intratracheal instillation of bleomycin. To inhibit the Wnt/β-catenin pathway, small interfering RNA (siRNA) for β-catenin was administered into trachea 2 h before bleomycin instillation and every 48 h afterward until sacrifice on day 14. The level of β-catenin expression was increased in the epithelial cells of bleomycin-administered mice. Intratracheal treatment with β-catenin siRNA significantly reduced β-catenin expression, pulmonary fibrosis and collagen synthesis in bleomycin-administered mice compared with controls, with no significant effect on the inflammatory response. The β-catenin-targeted siRNA also significantly decreased the levels of MMP-2 (P<0.01) and TGF-β (P<0.01) expression in the lung tissue. Blockade of the Wnt/β-catenin pathway by β-catenin siRNA decreased bleomycin-induced pulmonary fibrosis in the murine model. These findings suggest that targeting Wnt/β-catenin signaling may be an effective therapeutic approach in the treatment of IPF.

Potential role of the inflammasome-derived inflammatory cytokines in pulmonary fibrosis

Pulmonary fibrosis is a progressive, disabling disease with mortality rates that appear to be increasing in the western population, including the USA. There are over 140 known causes of pulmonary fibrosis as well as many unknown causes. Treatment options for this disease are limited due to poor understanding of the molecular mechanisms of the disease progression. However, recent progress in inflammasome research has greatly contributed to our understanding of its role in inflammation and fibrosis development. The inflammasome is a multiprotein complex that is an important component of both the innate and adaptive immune systems. Activation of proinflammatory cytokines following inflammasome assembly, such as IL-1β and IL-18, has been associated with development of PF. In addition, components of the inflammasome complex itself, such as the adaptor protein ASC have been associated with PF development. Recent evidence suggesting that the fibrotic process can be reversed via blockade of pathways associated with inflammasome activity may provide hope for future drug strategies. In this paper we will give an introduction to pulmonary fibrosis and its known causes. In addition, we will discuss the importance of the inflammasome in the development of pulmonary fibrosis as well as discuss potential future treatment options.

WNT/β-catenin signaling is modulated by mechanical ventilation in an experimental model of acute lung injury

PURPOSE

The mechanisms involved in lung injury progression during acute lung injury (ALI) are still poorly understood. Because WNT/β-catenin signaling has been shown to be involved in epithelial cell injury and hyperplasia during inflammation and sepsis, we hypothesized that it would be modulated by mechanical ventilation (MV) in an experimental model of sepsis-induced ALI.

METHODS

This study was a prospective, randomized, controlled animal study performed using adult male Sprague-Dawley rats. Sepsis was induced by cecal ligation and perforation. At 18 h, surviving animals were randomized to spontaneous breathing or two strategies of MV for 4 h: low tidal volume (V (T)) (6 ml/kg) plus 10 cmH2O of positive end-expiratory pressure (PEEP) versus high (20 ml/kg) tidal volume (V (T)) with zero PEEP. Histological evaluation, measurements of WNT5A, total β-catenin, and matrix metalloproteinase-7 (MMP7) protein levels by Western blot, and their immunohistochemical localization in the lungs were analyzed.

RESULTS

Sepsis and high-V (T) MV caused lung inflammation and perivascular edema with cellular infiltrates and collagen deposition. Protein levels of WNT5A, β-catenin, and MMP7 in the lungs were increased in animals with sepsis-induced ALI. High-V (T) MV was associated with higher levels of WNT5A, β-catenin, and MMP7 protein levels (p < 0.001), compared to healthy control animals. By contrast, low-V (T) MV markedly reduced WNT5A, β-catenin, and MMP7 protein levels (p < 0.001).

CONCLUSIONS

Our findings demonstrate that the WNT/β-catenin signaling pathway is modulated early during sepsis and ventilator-induced lung injury, suggesting that activation of this pathway could play an important role in both lung injury progression and repair.

Novel therapeutic approaches for pulmonary fibrosis

Pulmonary fibrosis represents the end stage of a number of heterogeneous conditions and is, to a greater or lesser degree, the hallmark of the interstitial lung diseases. It is characterized by the excessive deposition of extracellular matrix proteins within the pulmonary interstitium leading to the obliteration of functional alveolar units and in many cases, respiratory failure. While a small number of interstitial lung diseases have known aetiologies, most are idiopathic in nature, and of these, idiopathic pulmonary fibrosis is the most common and carries with it an appalling prognosis - median survival from the time of diagnosis is less than 3 years. This reflects the lack of any effective therapy to modify the course of the disease, which in turn is indicative of our incomplete understanding of the pathogenesis of this condition. Current prevailing hypotheses focus on dysregulated epithelial-mesenchymal interactions promoting a cycle of continued epithelial cell injury and fibroblast activation leading to progressive fibrosis. However, it is likely that multiple abnormalities in a myriad of biological pathways affecting inflammation and wound repair - including matrix regulation, epithelial reconstitution, the coagulation cascade, neovascularization and antioxidant pathways - modulate this defective crosstalk and promote fibrogenesis. This review aims to offer a pathogenetic rationale behind current therapies, briefly outlining previous and ongoing clinical trials, but will focus on recent and exciting advancements in our understanding of the pathogenesis of idiopathic pulmonary fibrosis, which may ultimately lead to the development of novel and effective therapeutic interventions for this devastating condition.

Alveolar epithelial cells express mesenchymal proteins in patients with idiopathic pulmonary fibrosis

Prior work has shown that transforming growth factor-β (TGF-β) can mediate transition of alveolar type II cells into mesenchymal cells in mice. Evidence this occurs in humans is limited to immunohistochemical studies colocalizing epithelial and mesenchymal proteins in sections of fibrotic lungs. To acquire further evidence that epithelial-to-mesenchymal transition occurs in the lungs of patients with idiopathic pulmonary fibrosis (IPF), we studied alveolar type II cells isolated from fibrotic and normal human lung. Unlike normal type II cells, type II cells isolated from the lungs of patients with IPF express higher levels of mRNA for the mesenchymal proteins type I collagen, α-smooth muscle actin (α-SMA), and calponin. When cultured on Matrigel/collagen, human alveolar type II cells maintain a cellular morphology consistent with epithelial cells and expression of surfactant protein C (SPC) and E-cadherin. In contrast, when cultured on fibronectin, the human type II cells flatten, spread, lose expression of pro- SPC, and increase expression of vimentin, N-cadherin, and α-SMA; markers of mesenchymal cells. Addition of a TGF-β receptor kinase inhibitor (SB431542) to cells cultured on fibronectin inhibited vimentin expression and maintained pro-SPC expression, indicating persistence of an epithelial phenotype. These data suggest that alveolar type II cells can acquire features of mesenchymal cells in IPF lungs and that TGF-β can mediate this process.

MicroRNAs in idiopathic pulmonary fibrosis

In this review, we describe the recent advances in the understanding of the role of microRNAs in idiopathic pulmonary fibrosis (IPF), a chronic progressive and lethal fibrotic lung disease. Approximately 10% of the microRNAs are significantly changed in IPF lungs. Among the significantly downregulated microRNAs are members of let-7, mir-29, and mir-30 families as well as miR-17∼92 cluster among the upregulated mir-155 and mir-21. Downregulation of let-7 family members leads to changes consistent with epithelial mesenchymal transition in lung epithelial cells both in vitro and in vivo, whereas inhibition of mir-21 modulates fibrosis in the bleomycin model of lung fibrosis. Perturbations of mir-155 and mir-29 have profibrotic effects in vitro but have not yet been assessed in vivo in the context of lung fibrosis. A recurrent global theme is that many microRNAs studied in IPF are both regulated by transforming growth factor β1 (TGFβ1) and regulate TGFβ1 signaling pathway by their target genes. As a result, their aberrant expression leads to a release of inhibitions on the TGFβ1 pathway and to the creation of feed-forward loops. Coanalysis of published microRNA and gene expression microarray data in IPF reveals enrichment of the TGFβ1, Wnt, sonic hedgehog, p53, and vascular endothelial growth factor pathways and complex regulatory networks. The changes in microRNA expression in the IPF lung and the evidence for their role in the fibrosis suggest that microRNAs should be evaluated as therapeutic targets in IPF.

Nuclear β-catenin is increased in systemic sclerosis pulmonary fibrosis and promotes lung fibroblast migration and proliferation

Pulmonary fibrosis is a disease that results in loss of normal lung architecture, but the signaling events that drive tissue destruction are incompletely understood. Wnt/β-catenin signaling is important in normal lung development, but whether abnormal signaling occurs in lung fibrosis due to systemic sclerosis and the consequences of β-catenin signaling toward the fibrogenic phenotype remain poorly defined. In this study, we show nuclear β-catenin accumulation in fibroblastic foci from lungs of patients with systemic sclerosis-associated advanced pulmonary fibrosis. Forced activation of β-catenin signaling in three independently derived sources of normal human lung fibroblasts promotes proliferation and migratory activities but is not sufficient to activate classic markers of fibroblast activation, such as TGF-β, type 1 collagen, α-smooth muscle actin, and connective tissue growth factor. These findings indicate that activation of β-catenin signaling in pulmonary fibroblasts may be a common feature of lung fibrosis, contributing to fibroproliferative and migratory activities associated with the disease.

Comparative proteomic analysis of lung tissue from patients with idiopathic pulmonary fibrosis (IPF) and lung transplant donor lungs

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal disease for which no effective therapy exists to date. To identify the molecular mechanisms underlying IPF, we performed comparative proteome analysis of lung tissue from patients with sporadic IPF (n = 14) and human donor lungs (controls, n = 10) using two-dimensional gel electrophoresis and MALDI-TOF-MS. Eighty-nine differentially expressed proteins were identified, from which 51 were up-regulated and 38 down-regulated in IPF. Increased expression of markers for the unfolded protein response (UPR), heat-shock proteins, and DNA damage stress markers indicated a chronic cell stress-response in IPF lungs. By means of immunohistochemistry, induction of UPR markers was encountered in type-II alveolar epithelial cells of IPF but not of control lungs. In contrast, up-regulation of heat-shock protein 27 (Hsp27) was exclusively observed in proliferating bronchiolar basal cells and associated with aberrant re-epithelialization at the bronchiolo-alveolar junctions. Among the down-regulated proteins in IPF were antioxidants, members of the annexin family, and structural epithelial proteins. In summary, our results indicate that IPF is characterized by epithelial cell injury, apoptosis, and aberrant epithelial proliferation.

An official ATS/ERS/JRS/ALAT statement: idiopathic pulmonary fibrosis: evidence-based guidelines for diagnosis and management

This document is an international evidence-based guideline on the diagnosis and management of idiopathic pulmonary fibrosis, and is a collaborative effort of the American Thoracic Society, the European Respiratory Society, the Japanese Respiratory Society, and the Latin American Thoracic Association. It represents the current state of knowledge regarding idiopathic pulmonary fibrosis (IPF), and contains sections on definition and epidemiology, risk factors, diagnosis, natural history, staging and prognosis, treatment, and monitoring disease course. For the diagnosis and treatment sections, pragmatic GRADE evidence-based methodology was applied in a question-based format. For each diagnosis and treatment question, the committee graded the quality of the evidence available (high, moderate, low, or very low), and made a recommendation (yes or no, strong or weak). Recommendations were based on majority vote. It is emphasized that clinicians must spend adequate time with patients to discuss patients' values and preferences and decide on the appropriate course of action.

The role of matrix metalloproteinases in cystic fibrosis lung disease

Significant airway remodelling is a major component of the increased morbidity and mortality observed in cystic fibrosis (CF) patients. These airways feature ongoing leukocytic inflammation and unrelenting bacterial infection. In contrast to acute bacterial pneumonia, CF infection is not cleared efficiently and the ensuing inflammatory response causes tissue damage. This structural damage is mainly a result of free proteolytic activity released by infiltrated neutrophils and macrophages. Major proteases in this disease are serine and matrix metalloproteases (MMPs). While the role of serine proteases, such as elastase, has been characterised in detail, there is emerging evidence that MMPs could play a key role in the pathogenesis of CF lung disease. This review summarises studies linking MMPs with CF lung disease and discusses the potential value of MMPs as future therapeutic targets in CF and other chronic lung diseases.

Scleroderma: from pathophysiology to novel therapeutic approaches

Systemic scleroderma may serve as a paradigm for orphan diseases where the rarity, different subsets and fluctuating disease activity constitute major obstacles of research into mechanisms and therapeutic development. Recently, significant advances in the detailed understanding of the functioning of growth factors, their receptors and of the physiology of the connective tissue have been achieved. In particular, an improved concept was developed for the pathophysiology of scleroderma, highlighting the role of hypoxia, cellular stress and a concert of interacting cytokines. Tyrosine kinases have been shown to regulate the activity of a number of cytokines and growth factors, e.g. transforming growth factor-beta and platelet-derived growth factor, which play a central role in the pathophysiology of SSc. Novel pharmacological compounds interacting with signalling cascades induced by hypoxia and intracellular signal transduction pathways of mesenchymal cells, e.g. tyrosine kinase inhibitors, are currently being investigated for the treatment of this life-threatening disease.

Bronchial blood supply after lung transplantation without bronchial artery revascularization

PURPOSE OF REVIEW

This review discusses how the bronchial artery circulation is interrupted following lung transplantation and what may be the long-term complications of compromising systemic blood flow to allograft airways.

RECENT FINDINGS

Preclinical and clinical studies have shown that the loss of airway microcirculations is highly associated with the development of airway hypoxia and an increased susceptibility to chronic rejection.

SUMMARY

The bronchial artery circulation has been highly conserved through evolution. Current evidence suggests that the failure to routinely perform bronchial artery revascularization at the time of lung transplantation may predispose patients to develop the bronchiolitis obliterans syndrome.

Chronic lung diseases

Chronic lung diseases often have high morbidity and mortality rate and have posed a serious threat to human health. The incidence of many chronic lung diseases such as asthma has been on the rise in the past decade, which causes serious economic burden. Despite many efforts which employed traditional experimental approaches to elucidate the mechanisms of the diseases have been made, little is known about the pathogenesis of complex lung diseases. Systems biology approaches which aim to integrate and analyze information gathered from multiple sources offer a great opportunity to examine complex human diseases from a new angle. Many attempts have been made using high-throughput technologies such as microarrays to study chronic lung diseases; although compared with the full-fledged systems biology approach, research strategies employed in most of these investigations still have much room to improve, promising findings have already emerged from these efforts, which demonstrates the potential of implementing systems biology in pulmonary biomedical research.

Resistance to bleomycin-induced lung fibrosis in MMP-8 deficient mice is mediated by interleukin-10

Background

Matrix metalloproteinases (MMPs) may have pro and antifibrotic roles within the lungs, due to its ability to modulate collagen turnover and immune mediators. MMP-8 is a collagenase that also cleaves a number of cytokines and chemokines.

Methodology and Principal Findings

To evaluate its relevance in lung fibrosis, wildtype and Mmp8^−/− mice were treated with either intratracheal bleomycin or saline, and lungs were harvested at different time points. Fibrosis, collagen, collagenases, gelatinases, TGFβ and IL-10 were measured in lung tissue. Mmp8^−/− mice developed less fibrosis than their wildtype counterparts. This was related to an increase in lung inflammatory cells, MMP-9 and IL-10 levels in these mutant animals. In vitro experiments showed that MMP-8 cleaves murine and human IL-10, and tissue from knockout animals showed decreased IL-10 processing. Additionally, lung fibroblasts from these mice were cultured in the presence of bleomycin and collagen, IL-10 and STAT3 activation (downstream signal in response to IL-10) measured by western blotting. In cell cultures, bleomycin increased collagen synthesis only in wildtype mice. Fibroblasts from knockout mice did not show increased collagen synthesis, but increased levels of unprocessed IL-10 and STAT3 phosphorylation. Blockade of IL-10 reverted this phenotype, increasing collagen in cultures.

Conclusions

According to these results, we conclude that the absence of MMP-8 has an antifibrotic effect by increasing IL-10 and propose that this metalloprotease could be a relevant modulator of IL-10 metabolism in vivo.

Bronchiolitis obliterans organizing pneumonia in Swine associated with porcine circovirus type 2 infection

Bronchiolitis obliterans organizing pneumonia (BOOP) is a chronic respiratory disease. Although the pathogenesis of BOOP is still incompletely understood, BOOP is responsive to steroids and has a good prognosis. In our five pigs with chronic postweaning multisystemic wasting syndrome (PMWS), typical BOOP lesions were revealed. All five porcine lungs showed typical intraluminal plugs, and porcine circovirus type 2 (PCV2) was identified. They also exhibited similar pathologic findings such as proliferation of type II pneumocytes and myofibroblasts (MFBs), extracellular collagen matrix (ECM) deposition, and fragmentation of elastic fibers. MFBs migration correlative molecules, for instance, gelatinase A, B and osteopontin, appeared strongly in the progressing marginal area of polypoid intraluminal plugs of fibrotic lesion. These molecules colocalized with the active MFBs. Both gelatinase activity and intercellular level of active MFBs were significantly increased (P < .05). Porcine chronic bronchopneumonia leads to BOOP and it is associated with PCV2 persistent infection. Swine BOOP demonstrates similar cellular constituents with human BOOP. Perhaps their molecular mechanisms of pathogenesis operate in a similar way. Thus we infer that the swine BOOP can be considered as a potential animal model for human BOOP associated with natural viral infection. Moreover, it is more convenient to obtain samples.

Tenascin-C deficiency attenuates TGF-ß-mediated fibrosis following murine lung injury

Tenascin-C (TNC) is an extracellular matrix glycoprotein of unknown function that is highly expressed in adult lung parenchyma following acute lung injury (ALI). Here we report that mice lacking TNC are protected from interstitial fibrosis in the bleomycin model of ALI. Three weeks after exposure to bleomycin, TNC-null mice had accumulated 85% less lung collagen than wild-type mice. The lung interstitium of TNC-null mice also appeared to contain fewer myofibroblasts and fewer cells with intranuclear Smad-2/3 staining, suggesting impaired TGF-β activation or signaling. In vitro, TNC-null lung fibroblasts exposed to constitutively active TGF-β expressed less α-smooth muscle actin and deposited less collagen I into the matrix than wild-type cells. Impaired TGF-β responsiveness was correlated with dramatically reduced Smad-3 protein levels and diminished nuclear translocation of Smad-2 and Smad-3 in TGF-β-exposed TNC-null cells. Reduced Smad-3 in TNC-null cells reflects both decreased transcript abundance and enhanced ubiquitin-proteasome-mediated protein degradation. Together, these studies suggest that TNC is essential for maximal TGF-β action after ALI. The clearance of TNC that normally follows ALI may restrain TGF-β action during lung healing, whereas prolonged or exaggerated TNC expression may facilitate TGF-β action and fibrosis after ALI.

Non-steroid agents for idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis is a chronic progressive lung disease with poor outcome and no effective treatment to date. This is an update of a Cochrane Review first published in 2003.

OBJECTIVES

To assess the efficacy of non-steroid agents in adults with idiopathic pulmonary fibrosis.

SEARCH STRATEGY

We searched the Cochrane Airways Group Register (30 March 2010), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1, 2010), Ovid MEDLINE to March week 5, 2010, EMBASE to week 13, 2010 and PubMed to April 2010, with additional handsearching, including abstracts of international conferences. We also contacted pharmaceutical companies and researchers in the field.

SELECTION CRITERIA

Randomised studies comparing non-steroid drugs with placebo or steroids in adults with idiopathic pulmonary fibrosis.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality, extracted data and assessed risk of bias. We contacted pharmaceutical companies to obtain missing information, if any. We combined survival outcomes using Peto odds ratios or hazard ratios (HR).

MAIN RESULTS

Fifteen trials involving 10 different drugs were included. Two trials enrolling 1156 patients compared interferon gamma-1beta with placebo: interferon gamma-1beta did not significantly improve survival (HR 0.88, 95% CI 0.47 to 1.64; P = 0.68). Four trials involving 1155 patients compared pirfenidone with placebo. Three trials, conducted in 1046 patients, provided data on progression-free survival: pirfenidone significantly reduced the risk of disease progression by 30% (HR 0.70, 95% CI 0.56 to 0.88, P = 0.002). Data on the effect of pirfenidone on pulmonary function could only be assessed for two studies analysing 314 patients. Forced vital capacity or vital capacity was significantly improved by pirfenidone (mean difference 0.08 L, 95% CI 0.03 to 0.13, P = 0.0006).

AUTHORS' CONCLUSIONS

Based on available data, partly still unpublished, pirfenidone appears to improve progression-free survival and, to a lesser extent, pulmonary function in patients with idiopathic pulmonary fibrosis. More data are needed on overall survival and quality of life on treatment. From the studies in this review, interferon gamma-1beta has not been shown to affect survival. Other agents evaluated in single studies either failed to provide evidence for a benefit or need to be assessed in larger randomised controlled trials.

Production and activation of matrix metalloproteinase 7 (matrilysin 1) in the lungs of patients with idiopathic pulmonary fibrosis

CONTEXT

Idiopathic pulmonary fibrosis (IPF) is characterized by diffuse interstitial inflammation and fibroblast proliferation with accelerated remodeling of extracellular matrix, which result in irreversible destruction of the lung's architecture.

OBJECTIVE

To elucidate the production levels, tissue localization, and activation of matrix metalloproteinase 7 (MMP-7) in the lungs of patients with IPF.

DESIGN

Bronchoalveolar lavage analysis was performed in 17 IPF patients and 6 healthy volunteers. Levels of MMP-7 in blood were assayed in 23 IPF patients and 20 controls. Histologic and immunohistochemical analyses were performed on paraffin sections of the lung tissues from patients with IPF, interstitial pneumonia associated with rheumatoid arthritis, or nonspecific interstitial pneumonia.

RESULTS

The proMMP-7 levels in bronchoalveolar lavage fluids from IPF patients were significantly higher than those from healthy controls, although there was no difference in the serum levels between the 2 groups. By immunohistochemistry, proMMP-7 was localized mainly to the hyperplastic alveolar and metaplastic bronchiolar epithelial cells in the lung tissues from IPF patients. Active MMP-7 was immunolocalized on alveolar macrophages and hyperplastic epithelial cells, which were also immunostained with antibody against CD151, a molecule associated with activation of proMMP-7. Immunoblot analysis indicated the overproduction of proMMP-7 together with a small amount of active MMP-7 in bronchoalveolar lavage fluids from IPF patients. The MMP-7 activity was detected in a cross-linked carboxymethylated transferrin film assay.

CONCLUSIONS

proMMP-7 is excessively produced by hyperplastic alveolar and metaplastic bronchiolar epithelial cells and activated locally in the lungs of IPF patients, suggesting that MMP-7 may contribute to the pathology of IPF.

Inhibition of Wnt/beta-catenin/CREB binding protein (CBP) signaling reverses pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF)/usual interstitial pneumonia is a ravaging condition of progressive lung scarring and destruction. Anti-inflammatory therapies including corticosteroids have limited efficacy in this ultimately fatal disorder. An important unmet need is to identify new agents that interact with key molecular pathways involved in the pathogenesis of pulmonary fibrosis to prevent progression or reverse fibrosis in these patients. Because aberrant activation of the Wnt/beta-catenin signaling cascade occurs in lungs of patients with IPF, we have targeted this pathway for intervention in pulmonary fibrosis using ICG-001, a small molecule that specifically inhibits T-cell factor/beta-catenin transcription in a cyclic AMP response-element binding protein binding protein (CBP)-dependent fashion. ICG-001 selectively blocks the beta-catenin/CBP interaction without interfering with the beta-catenin/p300 interaction. We report here that ICG-001 (5 mg/kg per day) significantly inhibits beta-catenin signaling and attenuates bleomycin-induced lung fibrosis in mice, while concurrently preserving the epithelium. Administration of ICG-001 concurrent with bleomycin prevents fibrosis, and late administration is able to reverse established fibrosis and significantly improve survival. Because no effective treatment for IPF exists, selective inhibition of Wnt/beta-catenin-dependent transcription suggests a potential unique therapeutic approach for pulmonary fibrosis.

Expression of matrix metalloproteases by fibrocytes: possible role in migration and homing

RATIONALE

Fibrocytes are progenitor cells characterized by the simultaneous expression of mesenchymal, monocyte, and hematopoietic stem cell markers. We previously documented their presence in lungs of patients with idiopathic pulmonary fibrosis. However, the mechanisms involved in their migration, subsequent homing, and local role remain unclear. Matrix metalloproteinases (MMPs) facilitate cell migration and have been implicated in the pathogenesis of pulmonary fibrosis.

OBJECTIVES

To evaluate the expression and role of matrix metalloproteinases in human fibrocytes.

METHODS

Fibrocytes were purified from CD14(+) monocytes and cultured for 8 days; purity of fibrocyte cultures was 95% or greater as determined by flow cytometry. Conditioned media and total RNA were collected and the expression of MMP-1, MMP-2, MMP-7, MMP-8, and MMP-9 was evaluated by real-time polymerase chain reaction. Protein synthesis was examined using a Multiplex assay, Western blot, fluorescent immunocytochemistry, and confocal microscopy. MMP-2 and MMP-9 enzymatic activities were evaluated by gelatin zymography. Migration was assessed using collagen I-coated Boyden chambers. Stromal cell-derived factor-1α and platelet-derived growth factor-B were used as chemoattractant with or without a specific MMP-8 inhibitor.

MEASUREMENTS AND MAIN RESULTS

Fibrocytes showed gene and protein expression of MMP-2, MMP-9, MMP-8, and MMP-7. MMP-2 and MMP-9 enzymatic activities were also demonstrated by gelatin zymography. Likewise, we found colocalization of MMP-8 and MMP-7 with type I collagen in fibrocytes. Fibrocyte migration toward platelet-derived growth factor-B or Stromal cell-derived factor-1α in collagen I-coated Boyden chambers was significantly reduced by a specific MMP-8 inhibitor.

CONCLUSIONS

Our findings reveal that fibrocytes express a variety of MMPs and that MMP-8 actively participates in the process of fibrocyte migration.

Matrix metalloproteinases, a disintegrin and metalloproteinases, and a disintegrin and metalloproteinases with thrombospondin motifs in non-neoplastic diseases

Cellular functions within tissues are strictly regulated by the tissue microenvironment which comprises extracellular matrix and extracellular matrix-deposited factors such as growth factors, cytokines and chemokines. These molecules are metabolized by matrix metalloproteinases (MMP), a disintegrin and metalloproteinases (ADAM) and ADAM with thrombospondin motifs (ADAMTS), which are members of the metzincin superfamily. They function in various pathological conditions of both neoplastic and non-neoplastic diseases by digesting different substrates under the control of tissue inhibitors of metalloproteinases (TIMP) and reversion-inducing, cysteine-rich protein with Kazal motifs (RECK). In neoplastic diseases MMP play a central role in cancer cell invasion and metastases, and ADAM are also important to cancer cell proliferation and progression through the metabolism of growth factors and their receptors. Numerous papers have described the involvement of these metalloproteinases in non-neoplastic diseases in nearly every organ. In contrast to the numerous review articles on their roles in cancer cell proliferation and progression, there are very few articles discussing non-neoplastic diseases. This review therefore will focus on the properties of MMP, ADAM and ADAMTS and their implications for non-neoplastic diseases of the cardiovascular system, respiratory system, central nervous system, digestive system, renal system, wound healing and infection, and joints and muscular system.

Mizoribine protects against bleomycin-induced lung injury

Bleomycin (BLM)-induced lung injury has become a model for studies of interstitial pneumonitis and pulmonary fibrosis. BLM induces lung injury in two phases: early inflammation characterized by infiltration of inflammatory cells into the lungs, followed by a late phase of fibrosis characterized by deposition of collagen. In this study, we examined the role of mizoribine (MZB) in the regulation of inflammatory tissue injury caused by BLM. We examined the role of MZB using a mouse model of BLM-induced lung injury. We demonstrated that mice subjected to instillation of BLM into the lungs had a significantly increased number of macrophages and lymphocytes in bronchoalveolar lavage fluid (BALF), but that those treated with MZB in the early phase showed a significant reduction in the total number of BALF macrophages and lymphocytes. However, MZB was unable to inhibit fibrosis in the late phase of BLM injury. Our findings suggest that MZB inhibits the proliferation of both lymphocytes and macrophages in the early phase of the BLM-induced acute inflammatory response, as well as its development and amplification, but does not inhibit fibrotic change in the late phase.

Abnormal expression of IGF-binding proteins, an initiating event in idiopathic pulmonary fibrosis?

For significant improvements to occur in the survival of patients with idiopathic pulmonary fibrosis (IPF), it is necessary to develop novel and more precisely targeted therapies. The selection of future appropriate regimens must critically depend on improved characterization of the molecules driving the pathogenesis of IPF. It is well defined that IPF is characterized by the expression of genes indicating an active tissue remodeling program, including extracellular matrix (ECM) and basement membrane components, as well as myofibroblast-associated and epithelial cell-related genes. A few recent advances are worth mentioning. Pulmonary research demonstrates abnormal expression of insulin-like growth factor (IGF) binding proteins (IGFBPs) in IPF, including human IPF bronchoalveolar lavage (BAL) cells and BAL fluids, human IPF fibroblasts, as well as fibrotic lung tissues of bleomycin-induced mice and IPF patients, analyzed by microarray, reverse transcription-polymerase chain reaction (RT-PCR), ribonuclease protection assay (RPA), Western blot, immunohistochemistry, or enzyme-linked immunosorbent assay (ELISA). Simultaneously, in vitro and in vivo studies indicate the involvement of IGFBPs in the initiation and development of the fibrosis process, including fibroblast activation and transdifferentiation to a myofibroblast phenotype, epithelial-mesenchymal transition (EMT), increased ECM production, and decreased ECM degradation, possibly contributing to the final lung fibrosis. These observations suggest that dysregulation of IGFBPs may be a key factor responsible for the initiation and perpetuation of IPF. Such efforts could lead to potential candidate molecules being exploited for therapeutic manipulation.

Inhibition and role of let-7d in idiopathic pulmonary fibrosis

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and usually lethal fibrotic lung disease characterized by profound changes in epithelial cell phenotype and fibroblast proliferation.

OBJECTIVES

To determine changes in expression and role of microRNAs in IPF.

METHODS

RNA from 10 control and 10 IPF tissues was hybridized on Agilent microRNA microarrays and results were confirmed by quantitative real-time polymerase chain reaction and in situ hybridization. SMAD3 binding to the let-7d promoter was confirmed by chromatin immunoprecipitation, electrophoretic mobility shift assay, luciferase assays, and reduced expression of let-7d in response to transforming growth factor-beta. HMGA2, a let-7d target, was localized by immunohistochemistry. In mice, let-7d was inhibited by intratracheal administration of a let-7d antagomir and its effects were determined by immunohistochemistry, immunofluorescence, quantitative real-time polymerase chain reaction, and morphometry.

MEASUREMENTS AND MAIN RESULTS

Eighteen microRNAs including let-7d were significantly decreased in IPF. Transforming growth factor-beta down-regulated let-7d expression, and SMAD3 binding to the let-7d promoter was demonstrated. Inhibition of let-7d caused increases in mesenchymal markers N-cadherin-2, vimentin, and alpha-smooth muscle actin (ACTA2) as well as HMGA2 in multiple epithelial cell lines. let-7d was significantly reduced in IPF lungs and the number of epithelial cells expressing let-7d correlated with pulmonary functions. HMGA2 was increased in alveolar epithelial cells of IPF lungs. let-7d inhibition in vivo caused alveolar septal thickening and increases in collagen, ACTA2, and S100A4 expression in SFTPC (pulmonary-associated surfactant protein C) expressing alveolar epithelial cells.

CONCLUSIONS

Our results indicate a role for microRNAs in IPF. The down-regulation of let-7d in IPF and the profibrotic effects of this down-regulation in vitro and in vivo suggest a key regulatory role for this microRNA in preventing lung fibrosis. Clinical trial registered with www.clinicaltrials.gov (NCT 00258544).

Lung transplant airway hypoxia: a diathesis to fibrosis?

RATIONALE

Chronic rejection, manifested pathologically as airway fibrosis, is the major problem limiting long-term survival in lung transplant recipients. Airway hypoxia and ischemia, resulting from a failure to restore the bronchial artery (BA) circulation at the time of transplantation, may predispose patients to chronic rejection. To address this possibility, clinical information is needed describing the status of lung perfusion and airway oxygenation after transplantation.

OBJECTIVES

To determine the relative pulmonary arterial blood flow, airway tissue oxygenation and BA anatomy in the transplanted lung was compared with the contralateral native lung in lung allograft recipients.

METHODS

Routine perfusion scans were evaluated at 3 and 12 months after transplantation in 15 single transplant recipients. Next, airway tissue oximetry was performed in 12 patients during surveillance bronchoscopies in the first year after transplant and in 4 control subjects. Finally, computed tomography (CT)-angiography studies on 11 recipients were reconstructed to evaluate the post-transplant anatomy of the BAs.

MEASUREMENTS AND MAIN RESULTS

By 3 months after transplantation, deoxygenated pulmonary arterial blood is shunted away from the native lung to the transplanted lung. In the first year, healthy lung transplant recipients exhibit significant airway hypoxia distal to the graft anastomosis. CT-angiography studies demonstrate that BAs are abbreviated, generally stopping at or before the anastomosis, in transplant airways.

CONCLUSIONS

Despite pulmonary artery blood being shunted to transplanted lungs after transplantation, grafts are hypoxic compared with both native (diseased) and control airways. Airway hypoxia may be due to the lack of radiologically demonstrable BAs after lung transplantation.

Serum MMP-7 is increased in diabetic renal disease and diabetic diastolic dysfunction

Circulating matrix metalloproteinase (MMP) levels may correlate with diabetic complications. Whether they are changed in early diabetic cardiomyopathy is not known and was examined in this study. TIMP-1 and collagen degradation products were also measured. Results from subjects with and without diastolic dysfunction were compared with those obtained for patients with varying stages of diabetic renal disease. Patients with type 2 diabetes with or without diastolic dysfunction with varying degrees of renal disease were recruited for this study. Age-matched non-diabetic subjects served as controls. MMPs (-1, -3 and -7) and TIMP-1 were measured by ELISA, MMP-2 and -9 by zymography and collagen degradation products by radioimmunoassay. Differences in the pattern of MMPs/TIMPs and collagen degradation products were observed. The most consistent change was in totalMMP-7, which was increased in those with diastolic dysfunction and those with macroalbuminuria. MMP-7 correlated with cardiac function (p<0.05 vs control, in those with diastolic dysfunction), and renal filtration function (p<0.05 vs control). In summary, we have identified novel relationships between serum MMP-7 and diabetic complications specifically in renal disease and in diastolic dysfunction. How increased circulating MMP-7 is associated with these diabetic microvascular complications and the significance of these findings will require prospective studies.

Integrative urinary peptidomics in renal transplantation identifies biomarkers for acute rejection

Noninvasive methods to diagnose rejection of renal allografts are unavailable. Mass spectrometry followed by multiple-reaction monitoring provides a unique approach to identify disease-specific urine peptide biomarkers. Here, we performed urine peptidomic analysis of 70 unique samples from 50 renal transplant patients and 20 controls (n = 20), identifying a specific panel of 40 peptides for acute rejection (AR). Peptide sequencing revealed suggestive mechanisms of graft injury with roles for proteolytic degradation of uromodulin (UMOD) and several collagens, including COL1A2 and COL3A1. The 40-peptide panel discriminated AR in training (n = 46) and test (n = 24) sets (area under ROC curve >0.96). Integrative analysis of transcriptional signals from paired renal transplant biopsies, matched with the urine samples, revealed coordinated transcriptional changes for the corresponding genes in addition to dysregulation of extracellular matrix proteins in AR (MMP-7, SERPING1, and TIMP1). Quantitative PCR on an independent set of 34 transplant biopsies with and without AR validated coordinated changes in expression for the corresponding genes in rejection tissue. A six-gene biomarker panel (COL1A2, COL3A1, UMOD, MMP-7, SERPING1, TIMP1) classified AR with high specificity and sensitivity (area under ROC curve = 0.98). These data suggest that changes in collagen remodeling characterize AR and that detection of the corresponding proteolytic degradation products in urine provides a noninvasive diagnostic approach.

New mechanisms of pulmonary fibrosis

The understanding of the pathogenesis of pulmonary fibrosis continues to evolve. The initial hypothetical model suggested chronic inflammation as the cause of pulmonary fibrosis, whereas a subsequent hypothesis posited epithelial injury and impaired wound repair as the etiology of fibrosis without preceding inflammation. Over the past decade, several concepts have led to refinement of these hypotheses. These include the following: (1) the importance of the integrity of the alveolar-capillary barrier basement membrane (BM) to conserving the architecture of the injured lung; (2) conversely, that the failure of reepithelialization and reendothelialization of this BM results in pathologic fibrosis; (3) transforming growth factor-beta is necessary but not sufficient to the pathologic fibrosis of the lungs; (4) the role of persistent antigens in the pathogenesis of usual interstitial pneumonia; and (5) the contribution of epithelial-to-mesenchymal transformation and bone marrow-derived progenitor cells in the pathogenesis of lung fibrosis. In this review, we will discuss these evolving conceptual mechanisms for the pathogenesis of pulmonary fibrosis relevant to idiopathic pulmonary fibrosis.